In high speed floor burnishing machines of the type with which the present invention is concerned, an electric motor drives a pad driver assembly which includes the floor burnishing pad at high angular velocities. Because the pad is driven in rotation, and because the pad is made of a very loosely woven fiber-like material and is highly permeable to the flow of air, there are centrifugal forces which tend to cause the material of the pad to "creep"--i.e., to move out from beneath the flexible backing plate which holds it. In this connection, the term "flexible" means that the material of the backing member is semi-rigid, but will normally flex under usage or can be flexed or bent with the hands.
The pad itself is held in place by teeth or projections beneath the backing member, and at least one improvement, described in the above-identified copending application, provides a retaining skirt or flange on the periphery of the backing member to help restrain pad creep.
Although these measures have extended the useful life of the pad by some measure, there nevertheless is room for improvement in that some pads are being discarded because they have lost their shape rather than because they have lost their ability to polish.
Briefly, the present invention provides for a plurality of apertures in the backing member as well as the gripping element. These apertures are spaced at equal angular increments about the backing member and at intermediate locations between the axis of rotation and the outer peripheral edge of the backing member. When the pad driver assembly is rotated at high speed, the apertures in the backing member permit air to flow downwardly into the pad itself. Because the pad is rotating at high angular velocity, the air is forced radially outwardly at an accelerating rate, thereby creating a slight vacuum beneath atmospheric pressure. Atmospheric pressure causes the outer peripheral portion of the backing member and the gripping element to press downwardly onto the pad material. This has the dual effect of causing the gripping element to engage and hold the pad material more effectively, thereby reducing the tendency of the pad material to creep, and it also applies pressure on the peripheral area of the pad which has the greatest burnishing effect because of the higher pad speed in that area.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.